For 22 weeks, participants followed either a low-fat, low-glycemic vegan diet or guidelines prescribed by the ADA. All 99 participants had type 2 diabetes. Both men and women participated and were recruited through a newspaper ad in the Washington, D.C., area.

Participants reported what they ate at the start of the trial and throughout the trial. Researchers took the data and calculated scores based on the Alternate Healthy Eating Index (AHEI). Scores were calculated at the beginning of the 22 weeks and again at the end. There was no difference in the scores between the two groups at the start of the study.

Past research has shown a correlation between AHEI and cardiovascular disease. The AHEI is a nine-component dietary index used to rate foods and macronutrients related to chronic disease risk. The higher the AHEI score, the lower the risk of cardiovascular disease. The vegan dieters saw significant improvements in their AHEI scores; the ADA group did not.

The vegan group improved significantly in every AHEI category, including increased intake of vegetables, fruits, nut and soy protein, and cereal fiber, and a decrease in trans fat intake.

Both groups were able to reduce their weight and their hemoglobin A1c, a measure of blood sugar levels over a prolonged period of time. However, the vegan group experienced more significant reductions in both categories.

"The results of this study suggest that, if followed for the long-term, a low-fat vegan diet may be associated with a reduced risk of major chronic diseases, particularly cardiovascular disease," the study concludes.

Neither diet resulted in adequate intake of vitamins D or E, or of calcium. Patients attempting to follow either eating plan should consult with their doctor and make sure they are getting adequate amounts of these nutrients.